In an electrical supply system, there are occasions when an alternate source of electric power is necessary or desirable. For example, the capability of switching from utility power to emergency generator power is important for businesses, hospitals and industries, and is also being employed in residential applications.
In certain applications, it is desirable for separate electrical circuits or even separate groups of electrical circuits to be arranged so that when one group of circuits is switched to a conductive state, another group of circuits is switched to a non-conductive state so as to prevent power supply to the circuits from two different power sources at the same time, e.g. from both a utility power supply and a generator power supply. In an arrangement such as this, a switch is typically provided for each power source to control the supply of electrical power. Accordingly, it is important to ensure that the switches are prevented from both being in the ON position at the same time, to ensure that power is supplied to the switch from only one power source.
Interlocks have been devised for preventing adjacent, aligned switches from both being in an ON position at the same time, to ensure that power is not supplied simultaneously from two different sources. Examples of such interlocks are disclosed in Flegel U.S. Pat. No. 5,648,646 issued Jul. 15, 1997, and in co-pending application Ser. No. 09/232,898, filed Jan. 15, 1999. The '646 patent discloses an interlock utilizing a linkage arrangement interconnected with opposite ends defined by each operating handle. The linkage applies a linear force between the operating handles when the handles are moved toward each other, to prevent the handles from simultaneously being in the ON position. This arrangement operates satisfactorily, but entails a number of components and requires interconnection with the switch handles. This can be a drawback, in that all switch handles may not have structure which facilitates connection with the ends of the switch handle, and prevents the same interlock from being used with switch handles of varying length.
The interlock disclosed in the '898 application utilizes a pair of base strips, each of which is engageable within a passage typically defined by the operating handle. The inner ends of the base strips are located adjacent each other between the handles, and a connector member is secured to the inner ends of the base strips to interconnect the base strips together. The connector member includes upstanding end portions, each of which faces one of the operating handles. The connector member end portions are configured so as to engage the handles and prevent both handles from being moved toward each other to the ON position at the same time. A screw or other guide member is mounted to the outer end of each base strip, and is adapted for receipt within a slot defined by the switch for guiding axial movement of the interconnected strips and connector member relative to the switches and operating handles. This construction is not physically interconnected with the handles and thus can be used with handles of varying widths so long as each handle defines a passage for receiving one of the strips.
It is an object of the present invention to provide a simplified interlock arrangement for a pair of aligned switches. It is a further object of the invention to provide such an interlock arrangement which relies upon a passage defined by each handle for mounting the interlock between the handles and for guiding axial movement of the interlock relative to the handles. Yet another object of the invention is to provide such an interlock arrangement which includes a more substantial interlock structure located between the operating handles as compared to the previous strip-type construction. Yet another object of the invention is to provide such an interlock arrangement which does not rely upon engagement within a slot defined by the switch for guiding movement of the interlock relative to the handles. A still further object of the invention is to provide such an interlock arrangement which is relatively simple in its components, construction and installation, yet which provides highly satisfactory operation in preventing adjacent, aligned switches from both being in an ON position at the same time.